Method of treating photographic material to obtain colored pictures



Patented Oct. 8, 1940 UNITED STATES METHOD OF MATERIAL TURES TREATINGPHOTOGRAPHIC TO OBTAIN COLORED PIC- Paul Goldfinger, Brussels-Uccle,Belgium, assignor to Bla. Gaspar, Brussels, Belgium No Drawing.

Application May'20, 1939, Serial No. 274,837. In Germany May 27, 1938 I4 Claims.

The present invention relates to a treatment bath for the production ofdye-images from uniformly dyed photographic silver imagesby treat- 1 ingsolutions that locally destroy the dye pres- 5 ent in the layer at theareas where metallic silver is present, and in proportion to thequantity of such silver. Aqueous solutions of hydrohalic acids arealready known as treatment solutions suitable for this purpose. It ismoreover known that the eflicacy of such baths may be intensified by theaddition of various chemicals; particu- (1) Hydrochloric acid 1.8% litre1 Potassium iodide grams.. 2.2 (2) Hydrochloric acid 1.8% litre 1Potassium iodide grams 2.2

2,3-dimethyl-quinoxaline; gram 1' (3) Hydrochloric acid 0.6%..-- litre 1Potassium iodide grams 3.3 2,3-dimethyl-quinoxaline "gram" 0.2

The increase in the efficacy of the new baths is shown by the followingcomparative test, viz.: 0.1% of dimethyl-quinoxaline is added to a0.51). hydrochloric acid. Metallic silver images dyedwith'Brillantbenzoechtgriin BL, Benzoazurine G (SchultzFarbstofftabellen, Leipzig 1931, 7th ed., vol. 1, No. 497) or withChrysophenin G (Schultz Farbstofftabellen l. e., No. 726) are treatedwith this solution and dye-images are obtained within about fourminutes. If the solution contains in addition such a, quantity ofpotassium iodide that in respect of this salt the solution is 1/ 7511silver images dyed in the same manner are converted to dye-images muchmore speedily and successfully, i. e., in about one minute. A silverimage dyed red with Supranolbrillantrot B (Schultz Farbstoiftabellen,Leipzig 1932, 7th ed., vol. 2,

page 204) when treated for six minutes in a bath without the addition ofpotassium iodide yields but an unsatisfactory dye-image, whereas a gooddye-image is obtained within three minutes if a bath containing thepotassium iodide is employed. Even the addition of a much smallerproportion of potassium iodide, say one-five-hundredth mol per litre, isstill effective.

56 The dyes cited above are to be understood as but examples; suitabledyes are also the other known dyes used in the art, in particular azodyes, such as the .yellow Xylenwalkgelb G (Schultz Farbstofftabellen,Leipzig 1932, 7th ed., vol. 2, page 232), the blue Diaminreinblau FF 6(Schultz Farbstofftabellen, Leipzig 1931, 7th ed., vol. 1 No. 510) andthe red Polarbrillantrot B (Schultz Farbstoiftabellen, Leipzig 1932, 7thed., vol. 2, page .An addition to the bath of hydrobromic acidorbromides also is effective, 10 but to a'less degree than hydroiodicacid. On the other hand; the addition of hydroiodic acid to ahydrobromic acid bath' is even more -eifectivethan to a hydrochloricacid solution, for the hy-. drobromic acid treating baths are inthemselves 15 more effective than hydrochloric acid solutions. However,in view of the question of greater econ-' omy, the tests as to theaccelerating effect were mainly carried out in connectionwithhydrochloric acid baths. 20

In the course of these experiments, other chemicals were tested as totheir accelerating effect,

and it was found that not only iodides and bro-p mides, but alsosulphocyanides, such as am-' monium-sulphocyanides and thiocarbamide,in- 25 I crease the efiect of a hydrochloric acid bath. Theseexperiments werecarried out with a 0.5n hydrochloric acid, to which wasadded 0.1% of dimethylquinoxaline and in addition either 0.01 mol ofthiocarbamide or 0.01 mol of ammonium so sulphocyanide or 0.01 mol ofpotassium. bromide for each litre of solution. In the case of the silverimage dyed with Diaminreinblau FF, the bath containing thiocarbamidehadthe speediest effeet. When the images were dyed with Benzol- 5 ichtrot(Schultz Farbstofftabellen, Leipzig 1931, 7th ed., vol. 1, No. 566) orwith Brillantbenzoechtgriin BL, it turned out that potassium bromide andammonium sulphocyanidehad the greatest accelerating effect. On the otherhand, in every 40 experiment it was found that the effect ofthiocarbamide, sulphocyanide and bromide was surpassed by the effect ofthe iodide. The effect of the additional component to the bath appearsto be due to'the fact that the substances used, and

especially the hydroiodic acid, reduce" the con-, centration of freesilver ions in the aqueous solution to a greater extent than does thehydrochloric acid. 1

-It will probably also be due to this fact that the hydroiodic acid orother substance added to the solution may be employed in such a quantitythat the hydrochloric acid is present in an excess to the equivalentamount of the added substance. When using hydroiodic acid as theaddition toss hydrochloric acid, useful baths were obtained when theconcentration of the solution in respect of hydrochloric acid was from0.111, to normal, and in respect of hydroiodic acid from 0.00211. to0.1n. It follows as a matter of course that higher or lowerconcentrations are quite possible,

' and that the limits mentioned above designate only a range ofconcentration that is to be recommended for practical purposes.

What is claimed is: v 1. For the production of colored photographicpictures by means of local destruction of the dye at areas wheremetallic silver is present in photographic layers uniformly dyed withreduci-- ble dyes, a treating bath comprising an acid aqueous solutionof hydrochloric acidvand hyd'roiodic acid, the concentration of chlorideions ranging from 0.1 normal to 1.0 normal, the concentration of iodideions ranging from 0.002 normal to 0.1 normal.

2. For the production, of colored photographic pictures by means oflocal destruction of the dye at areas where metallic silver is presentin photographic layers uniformly dyed with reducible dyes, a treatingbath comprising an acid aqueous solution of hydrochloric acid andhydroiodic acid, the concentration of'chloride ions ranging from 0.1normal to 1.0 normal, the concentration of iodide ions ranging from0.002 normal to 0.1' normal, the bath further comprising a small amountof dimethyl-quinoxaline.

3. For the production of colored photographic pictures by means of localdestruction of the dye at areas where metallic silver is present in;

photographic layers uniformly dyed with reducible dyes, a treating bathcomprising hydroiodic acid and hydrochloric acid in an at least ten-foldexcess to the equivalent amount of hydroiodicacid, the concentration ofthe iodide ions ranging from 0.002-normal to 0.1-normal.

4. For the production of colored photographic pictures by means of localdestruction of the dye at areas where metallic silver is present in

